[Mgs] MGB rear brakes

Simon Matthews simon.d.matthews at gmail.com
Mon Feb 23 15:05:03 MST 2009


It's not about the amount of fluid, it's about the force applied. With
a larger diameter slave cylinder, the same pressure is  applied to a
larger area, resulting in a greater force. Hence greater braking
effort.

The fluid will move in a manner that equalizes the pressure throughout
the system (barirng pressure limiters or other features).

Vehicles used to have pressure limiters on the rear brakes, allowing a
greater rear/front braking effort ratio under normal (not emergency)
braking -- I don't know if this is still the case now ABS brakes are
almost universal.

Simon

On Mon, Feb 23, 2009 at 12:53 PM, Max Heim <max_heim at sbcglobal.net> wrote:
> I am inclined to agree with your thinking. For instance, truck rear wheel
> cylinders are often larger than a similar-sized passenger car, for the
> reason you state -- to apply proportionally less shoe motion per inch of
> pedal travel to the rear brakes, to avoid rear wheel lockup when unloaded.
>
> In an example from another genre, people that upgrade the rear axles in
> Mopar A-bodies (to 8.75 from 7.25 ring gear) often compensate for the larger
> rear drums (to 10" from 9") by fitting Dodge truck rear wheel cylinders (to
> 7/8" from 3/4").
>
> By that logic, the rear-heavy MGB-GT should have had SMALLER diameter rear
> wheel cylinders. On the other hand, the nose-heavy MGC may have had larger
> cylinders.
>
> Were those MGC-GT rear cylinders, possibly?
>
>
>
> on 2/23/09 12:03 PM, Norm 2Bs at twobees at sprynet.com wrote:
>
>> It has been 2 years since my MGB & I parted company.  But, if my failing
>> memory serves me right, I used the larger GT rear cylinders on my '66
>> roadster BECAUSE I raced it.  The theory was, the master puts out x-volume
>> of brake fluid.  A larger wheel cylinder is moved less given that volume.
>>
>> As I said, I'm no longer certain of that.  But, in the years I raced the B,
>> I never had problems with over-braking at the rear - neither on the track or
>> on the street.  Only time I remember locking up was in Turn 1 at The Glen.
>> Then all 4 locked up.  Generally, I could out-brake almost all of the cars
>> in my race group with that setup & Hawk pads on the front & metallic shoes
>> on the rear.
>>
>> Norm Sippel
>> '59 Turner
>> '60 Alfa
>
>
>
>
> --
>
> Max Heim
> '66 MGB GHN3L76149
> If you're near Mountain View, CA,
> it's the primer red one with chrome wires
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